You are correct, however generally we are not concerned with testing the coil by swapping the wire, only the wire. #3 and 4 are the same length, that is the reason I recommended swapping them. Swapping coils left to right is the only way to test the coils definitively.

 

Just removed #4 plug. It has been in engine for a week or 2. Should it look like this?
Gap is a little lower than the range that was specified. I believe 0.8 mm. I will check and post.
oh yeah replaced this plug with a new identical.
Still miss fire on #4.

 

Thanks for all the help. I'll begin trying your suggestions.

 

Checked the gap for the plug. It is 0.8 mm or 0.031

 

Spark plug insulator should not be so black, but not caused by small gap. After a couple weeks, the insulator should still be nearly white. While you are in there at the coils, be sure to double check the HT leads are all going to the correct plugs and coil terminals, and don't get confused by the numbers on the coils.

 

can I just swap wires with 4 and 6? Much easier to get to.

 

So, the basic concept is to move the bad part to a different location, swapping it with a known good part. That way the misfire should move to a different location. It does not really matter which known good part is used, so long as they fit, in cases of multiple similar parts (like spark plug wires). The problem with swapping in a "new" part is that it could actually be bad, since it has not been proven good on the engine. That is why the method uses parts already on the engine. It is a disciplined approach, without shortcuts, that is guaranteed to find bad parts if closely followed.